Automatic crimping presses have long been used in the connector industry to effect high-speed mass termination of various cables. FIGS. 1 and 2 are side and front views, respectively, of one exemplary automatic crimping "T-terminating unit" Model No. 768793 which is commercially available from AMP, Inc..RTM. In general, such presses include a reciprocating ram group 1 which is driven by an electric motor 3 through a torque multiplication mechanism 5. Various crimping tool-heads may be secured to the underside of ram group 1, and the attached tool head is driven with the ram group into proximity with a continuous-feed applicator, shown generally as 8, which tenders the terminal(s) to be crimped.
Significant torque multiplication is necessary to generate a sufficient downward force for the crimping operation, and this is accomplished in the illustrated machine by a pulley-driven torque multiplication mechanism 5. More specifically, the electric motor 3 is housed on a lower shelf of the illustrated press. The motor 3 drives a pulley 4 which is housed in the rear of the press. The pulley 4 drives a belt 7 which extends upwardly and encircles a large flywheel 9, which in turn drives a cylindrical crank shaft through a clutch enclosed in flywheel 9. The crank shaft is rotatably seated in the upper section of the press and runs to the front of the press. An offset crank pin 2 protrudes forwardly from an end face of the crank shaft. The crank pin 2 is offset from the rotation axis of the crank shaft and orbits about the axis as the crank shaft is rotated.
The conventional automatic crimping presses are of a push link design wherein the crank pin 2 is directly coupled to a push link 6, which is in turn coupled to a ram 20 through a ball joint and socket 11. The crank pin 2 compresses the push link 6 and ram 20 downwardly during 180.degree. of its orbit to advance the entire ram group 1 and crimping tool head toward the applicator 8. This illustrated press and its commercial counterparts do not allow convenient adjustment of the crimp height to compensate for such things as tooling wear, dimensional tolerances of replacement parts, and dimensional changes due to temperature variations. Furthermore, the current configuration of the ram group 1 renders it difficult to incorporate a suitable retrofit adjustment feature.
Moreover, although the ram group 1 is reciprocated over a distance equal to a stroke length of the crank pin 2 which may be, for example, 1.625", the terminals are crimped in a crimping zone which extends only over a final portion of the downward displacement of the ram group, i.e., the final 0.1" of the downward displacement. Force required to displace the ram group 1 is relatively low except during actual crimping of the terminal, when forces on the order of several thousand pounds are required to deform the terminal. A greater mechanical advantage of the ram drive could be achieved by extending the portion of rotation of the crank pin 2 during which actual crimping occurs, thereby reducing a size requirement for the motor 3. Therefore, it would be desirable to concentrate most of the ram displacement during the early portion of the crank pin rotation away from top dead center so that a larger portion of the crank pin rotation could be devoted to performing the actual crimping. However, the existing push link design tends to produce a majority of the downward ram displacement during the final 90.degree. of downward rotation of the crank pin, as shown by a plot of ram displacement versus crank pin rotation in FIG. 6. The plot of ram displacement versus crank pin rotation can be altered by altering the length of the push link, but at best, the push link design can only be made to produce an equal displacement of the ram during the initial 90.degree. of crank pin downward rotation and the final 90.degree. of crank pin downward rotation, i.e., a pure sinusoidal motion. It would be advantageous to provide a crimping machine which produces a majority of the ram displacement during the initial 90.degree. of crank pin downward rotation in order to increase the angle of crank pin rotation devoted to performing the crimping. The present invention accomplishes this by employing a tensioned linkage to pull the ram downward rather than compressive force on a push link. The present invention also facilitates the OEM or retrofit addition of a crimp height adjustment feature.